The auto industry said Monday that lawsuits over vehicles' greenhouse gas emissions could eventually force manufacturers to eliminate big SUVs from the market in California, an assertion denied by environmental attorneys and the state air quality board.

"If we lost (in court)," said Dave Barthmuss, General Motors' spokesman for environmental and energy affairs, "certain vehicles could not be offered for sale -- vehicles that consume more fuel than others. There would be fewer SUVs and we might not be able to offer them for sale in California. It could spell the end of the big SUV in California."

At the California Air Resources Board, however, spokesman Jerry Martin said the 2002 law in question cannot force the auto industry to reduce the size of its vehicles or to abandon any models it wants to keep selling.

The spat over what may happen to SUVs in California stems from a pair of federal court lawsuits that have been going on for years but are back in the news because one of them is scheduled to be argued Wednesday before the U.S. Supreme Court.

In that case, California, along with 11 other states and several environmental organizations, wants federal limits on vehicle emissions of greenhouse gases. In another case, filed in federal court in Fresno two years ago, the auto industry challenged the 2002 California law requiring new vehicles sold in the state to cut tailpipe emissions by 30 percent by 2016. The law is to be phased in, starting in 2009.

If the Supreme Court rejects states' right to sue the Environmental Protection Agency to limit greenhouse gases, legal experts doubt that California can prevail in the other lawsuit over its 2002 emissions law.

The crux of both legal issues revolves around the strong differences between the auto industry, on the one hand, and the lawsuit-filing states and environmental organizations, on the other, over what causes pollution and global warming and what can be done about it.

The backdrop of this drama is that for decades California has led the nation in devising tougher emissions laws. For a long time, so-called "49-state cars" with less stringent smog controls were sold in all states but California, where only cleaner cars were put on the market.

Finally, the industry, acknowledging California's dominant position in the marketplace, as well as the fact that other states have enacted equally tough smog laws, started making all cars alike.

The issue now, according to Josh Dorner, spokesman for the Sierra Club, one of the groups suing the EPA in the case to be heard Wednesday, is "whether the EPA can regulate global warming from car (emissions.) The Bush administration is saying that the EPA doesn't have that authority and even if it did, it would be a bad idea to regulate global warming."

G.M.'s Barthmuss said the efforts by California and the 11 other states to be able to limit greenhouse gas emissions "is really a state attempt to try to regulate fuel economy, because the way you reduce greenhouse gases is to reduce the amount of fuel you burn." Fuel economy regulation, Barthmuss said, is the responsibility of the federal government and should be handled only by the federal government.

David Doniger, the Natural Resources Defense Council attorney handling the case being heard before the Supreme Court, said the big problem is that the federal government refuses to allow for flexibility when seeking solutions to pollution and global warming problems.

"You can reduce emissions and at the same time reduce fuel consumption through better fuel injection, better transmissions, and improved engine design and electronic controls on fuel systems," Doniger said. "All of these tend to reduce conventional emissions and greenhouse gas emissions."

Doniger also said auto industry fears that SUVs would be sent to the elephants' graveyard were largely groundless. He said that when the 2002 law was passed, the air resources board had a "duty to lay out one feasible pathway, by which you build a car that has X and Y and Z on it and it will meet those standards."

The law was designed to enable the industry to "build SUVs, pickups and vans without downsizing," Doniger said. "You'd have to change engine and transmission combinations -- there was a mandate from the (state) Legislature to reduce emissions where technically and economically feasible."

He said that by the year 2016 these changes would add about $1,000 to the retail cost of each vehicle, but "the fuel savings that went along with lower emissions would pay that back."